Downlink Precoding for Multi-Beam LEO Satellite Communications with Asynchronous Interference

Direct-to-smartphone is becoming a popular direction of low earth orbit (LEO) satellite communications. In this paper, we investigate the downlink (DL) precoding method for multi-beam LEO satellite communication systems with asynchronous interference. Specifically, we first establish the channel model revealing that the transmitting signals between different beams are asynchronous and further derive the expression of asynchronous interference. Then, we propose a DL precoding method based on maximizing the average signal-to-leakage-plus-noise ratio (ASLNR) with statistic channel state information (CSI). The simulation results demonstrate the significant improvements of the proposed precoding method in the system sum rate.